Heart attack triggers more likely in night owls than early birds: study

By Stephen Beech via SWNS

A potential heart attack trigger is almost twice as common in people who burn the midnight oil compared to early birds, according to a new study.

Swedish researchers found far more evidence of artery calcification in night owls.

Atherosclerosis involves fatty deposits accumulating on the inside of the arteries, making it harder for blood to pass through.

The disease develops over a very long period of time and is not noticed until it leads to blood clots causing angina, a heart attack or stroke.

Previous research has shown that people with late-night habits have an increased risk of cardiovascular disease.

But the new study, published in the journal Sleep Medicine, is the first to show how circadian rhythms specifically affect calcification of the arteries.

The study involved more than 700 Swedish men and women aged between 50 and 64.

The degree of artery calcification in the heart’s coronary arteries was examined using computer tomography.

Participants themselves indicated their "chronotype" on a five-point scale: extreme morning type, moderate morning type, intermediate type, moderate evening type, or extreme evening type.

Of the 771 participants, 144 identified as extreme morning types, and 128 as extreme evening types.

The researchers explained that each chronotype has an average time when half of the night's sleep has passed.

In a previous study involving the same group, though not necessarily the same individuals, that time occurred at 2.55 am for the extreme morning type group and at 4.25 am for the extreme evening type group.

With the remaining chronotype groups’ mid-sleep times were somewhere in between those extremes.

Among those who were most alert in the morning, just over one-in-five (22.2 percent) had "pronounced" artery calcification – the lowest proportion of all five chronotypes.

But the extreme evening type group had the highest prevalence of severe coronary artery calcification, at 40.6 percent.

Study first author Mio Kobayashi Frisk, of Sahlgrenska Academy, University of Gothenburg, said: “Our results indicate that extreme evening chronotype may be linked not only to poorer cardiovascular health in general, but also more specifically to calcification in the coronary arteries calcification and atherosclerosis."

The statistical analysis considered a range of other factors that can affect the risk of atherosclerosis, including blood pressure, blood lipids, weight, physical activity, stress level, sleep, and smoking.

Co-author Dr. Ding Zou, a researcher at Sahlgrenska Academy, said: “As well as the previously known factors, the individual circadian rhythm also appears to be an important risk factor for atherosclerosis."

Dr. Zou added: "We interpret our results as indicating that circadian rhythms are more significant early in the disease process.

"It should therefore particularly be considered in the preventive treatment of cardiovascular diseases."